1. Field of the Invention
The present invention relates generally to materials which are designed to be used as substitutes for concrete. More particularly, the present invention involves non-cementious polymer-based materials which exhibit many of the desirable properties of concrete while at the same time eliminating some of the properties of concrete which are undesirable in certain situations.
2. Description of Related Art
Concrete is one of the most common building materials. It is widely available and is relatively inexpensive. It can be used alone or, more commonly, with some type of reinforcements embedded in the concrete structure. In spite of its popularity, normal concrete does have a number of drawbacks. For example, the compressive strength of normal concrete is only on the order of 3 to 4 kilogram per square inch (ksi) and the tensile strength is around only 0.3 ksi. In addition, the relatively high density of concrete (2.3 grams per cubic centimeter) makes it too heavy for many applications where light weight and structurally strong building materials are required.
Polymers have been used as additives to enhance various properties of concrete. These cement-based compositions include varying amounts of polymer additives which are included in the concrete mixture to improve properties such as plasticity and adhesion. For example, see U.S. Pat. Nos. 5,109,088; 4,939,191; and 3,415,773 wherein various cement-polymer compositions are described. In addition, there has been interest in producing non-cementious (i.e. cement-free) materials which may be used in place of concrete. For example, polymer-based materials which have been proposed as non-cementious replacements for concrete are described in U.S. Pat. Nos. 5,461,112.
There are a few problems among the many advantages of using polymer-based materials in place of concrete. For example, many polymers will burn if they are not specially treated. This is a significant drawback when compared to concrete structures which are fireproof. In addition, most polymer blends cure exothermically. As a result, it is difficult to cast many large polymeric structures without causing rapid and uncontrollable heat release which causes rapid and uncontrollable curing that may result in thermal damage or fire. Concrete, on the other hand, may be cast in massive structures which cure relatively slowly with only a minimum amount of heat release. In addition, concrete is relatively slow curing so that relatively large structures may be formed in one pouring.
In view of the above, there is a present and continuing need to develop non-cementious concrete-like materials which are fire resistant and have greater mechanical properties than concrete. Further, such concrete-like materials should be capable of being cast and cured as large structures without uncontrollable exotherms.